Pulse combustion drying is a recognized technique for effecting heat processing of particulate material. Illustrative of some prior art techniques are U.S. Pat. Nos. 3,618,655; 4,226,668; 4,226,670; 4,265,617 and 2,838,869.
Typically, pulse combustors require an acoustic resonator. Such combustors have high local combustion intensity and high local heat release. However, they also are subject to limited pressure gain and require a large resonator volume.
Broadly, pulsed combustors or burners resemble a two cycle gasoline engine, in which fuel and air are sucked into a combustion chamber, the mixture is caused to explode and then exhausted from the combustion chamber for its intended use. When the mixture explodes the pressure in the combustion chamber increases greatly and, typically, closes a flapper valve or the like thereby preventing both continued inflow of the mixture and outflow of products of combustion in the upstream direction. Where no valve is used a resonant chamber downstream of the combustion chamber provides more or less the same result. Under this condition, the combustion gas is exhausted through the resonator to the point of use, thereby creating a negative pressure which permits entry of a new quantity of the mixture in the combustion chamber and the cycle is then repeated.